Mounting evidence supports our 1971 hypothesis that rodents and humans share common embryonic, cell surface antigens conserved in evolution. The discovery of protooncogenes and their possible expression in central events in embryogenesis and fetal development in metazoans bespeak the key role of so-called fetal gene products in growth control of normal and abnormal (tumor) cells. The proposed work seeks to characterize the immunochemical properties of several oncofetal antigens we have recently desribed with the aid of monoclonal antibodies we developed in a syngeneic mouse system. Several polypeptides detected with these monoclonal antibodies are unique to tumor-associated immunoprecipitates described by others in certain human tumors. Polypeptides of 23, 44 to 46 and 200 kilodaltons which react with our monoclonal antibodies prepared against syngeneic rodent fetus, will be analyzed immunochemically to characterize their epitopes and to determine their relatedness to determinants on fetal and tumor cells of mice and men that induce tumor-associated transplantation resistance against syngeneic mouse tumors induced by viruses and chemicals. The epitopes selected for study have been shown to be expressed on a spectrum of rodent and human tumors using absorption ELISA methods and affinity gel immunochromatography and SDS-PAGE analysis. They also appear in midgestational fetal tissues of rodents and man but not in term fetal tissues or any adult tissue examined. The fetal tissues displaying these antigens will be identified by cell sorting. Studies to characterize the biochemistry or antigen phasing in fetus and the relationship to protooncogene products to the selected oncofetal polypeptides will be initiated. (AG)